Vision loss is disruptive to the individual affected, their family and society. There are many causes of vision loss and vision impairment. Many of these conditions however are treatable if detected earlier.
Age-related macular degeneration (AMD) is a leading cause of irreversible legal blindness in the western world. Over 12 million Americans have some type of AMD, and millions of others suffer from other retina issues. Currently, home self-monitoring tools for retina diseases fail to adequately indicate a changing vision, resulting in delayed treatment and higher incidences of severe vision loss.
Other ophthalmic conditions ranging from refractive error to cataracts to glaucoma also respond to intervention. Unfortunately, many people affected by these disorders suffer needlessly because they are either unaware of their condition or they do not respond to their symptoms with sufficient promptness. This often leads to a delay in presentation after the onset of a visual change, which creates a delay in clinical diagnosis and therefore a delay in the start of treatment. This delay may lead to more severe vision impairment, or even permanent and unrecoverable vision loss.
Furthermore, for a variety of occupations, visuals tests have been proposed for the assessment of various aspects of visual performance. For example, color vision screening has previously been used as a means for detecting color deficiencies, and as a means for assessing the severity of a user's color vision loss.
Color vision testing has also been used to determine whether a user's vision meets the color vision requirements for a given occupation (e.g. aviation, transportation, or police and fire services); to assist in the detection of diseases (such as diabetes or multiple sclerosis) that can affect visual performance; to assist in the diagnosis of specific diseases of the eye (e.g. optic neuritis, age related macular degeneration, photoreceptor dystrophies, etc.); to facilitate disease management and treatment monitoring; and to enable the monitoring of eye-related side-effects in pharmaceutical drug trials.
One classic illustrative vision test involves the measurement of high contrast Visual Acuity (VA). Visual Acuity is a quantitative assessment of the ability to resolve high contrast optotypes. In the United States, the measurement is recorded in a ratio, such as 20/20, 20/40, 20/200, and so on. The ratio 20/20 indicates that at 20 feet, an individual is able to resolve a high contrast black letter which subtends 5 minutes of arc against a white background. From a test distance of 20 feet away, the 20/20 letter is 8.87 mm tall. The ratio 20/40 indicates that the individual can resolve a letter which is twice the size as the 20/20 benchmark. The ratio 20/200 means that the individual can resolve a letter that is ten times the size as the 20/20 benchmark.
In a visual acuity test, a user is asked to locate the orientation of the gap in a Landolt C optotype. The user's visual acuity is assessed on the basis of the smallest, high contrast Landolt C for which the user can resolve and locate the orientation of the gap. The test is carried out with both bright and dark targets and the results provide a measure of visual acuity similar to that measured with Snellen letter charts in optometric practices, but with improved accuracy and the use of a single target. The test can also be used to assess the effect of “visual crowding” when the test target is surrounded by other targets.
These types of tests are usually undertaken by displaying computer generated images to a subject via a monitor, typically a cathode ray tube, liquid crystal display, or a projector. The patient attends to the images presented on the display and responds to the stimuli they observe on the screen. For example, in a test where the user might be required to identify the location of a gap in a Landolt C optotype, the user may be required to respond accordingly to the quadrant of the image (top left, bottom left, right or bottom right) in which the gap in the Landolt C optotype is located. Once the user has responded to the particular image being displayed, a new image is presented to the user to which the user responds. This process continues until a series of optotypes of varying sizes have been presented and corresponding patient responses have been noted. The computer program then determines the user's visual performance based on their responses to the image displayed.
Government agencies use visual acuity guidelines for several matters. The Department of Motor Vehicles, for example, uses visual acuity to determine eligibility for motorist licensure. The Internal Revenue Service uses visual acuity to determine whether the taxpayer is legally blind in allowing an increased standard deduction on the federal tax return. Certain occupations, for example pilots and law enforcement, have a minimum visual acuity requirement. Schools frequently have nurses administer visual acuity measurements at specific grade levels to detect reduced vision, which can interfere with academic and athletic performance. Visual acuity is also routinely measured during routine physical exams. Reduced visual acuity can signal uncorrected refractive error, which can be managed with glasses, contacts, or refractive surgery. It can also signal conditions such as amblyopia and the presence of diseases such as cataracts, glaucoma, and macular degeneration. For these collective aforementioned reasons, there is consumer interest in having the ability to perform a self-guided visual acuity screening. Moreover, due to some perceived burden and associate costs, most consumers delay in scheduling an eye examination for obtaining baseline vision information. Therefore, a visual acuity examination that can be self-administered at any time and any place, such as that disclosed by the present invention, is practical, useful and preventive of many eye related conditions and diseases.
While older known systems have been shown to be effective in vision testing and have accurately assessed the patients' visual performance, it is generally the case that the equipment (in particular the display) required to perform these tests is typically large and expensive, and hence tends to only be accessible at hospitals or research centers. As the equipment may not to be easily and universally available, patients may neglect to travel to a facility to undertake these tests. Furthermore, in less developed regions of the world, traveling to these facilities can be problematic for less able users. The use of such other tests for mass screening of eye conditions, on a regular basis is therefore very limited.
It is also the case that in less developed regions of the world, the cost of equipment is such that some hospitals may simple forego with the purchase of the equipment when possible. One unfortunately consequence of this is that many patients continue to endure conditions that could perhaps be treated if their vision were to be properly screened and investigated.
It would be highly advantageous, therefore, if a simple and free method of vision screening could be proposed, wherein this method would be more accessible to patients and would be more likely to be implemented on a wider scale. Simple vision screening could be mitigated through properly devised testing apparatus and method that utilized commonly available visual equipment (such as a cellular phone screen, tablets, iPad screen, or any screen touch devices) for the display of tests to users. Vision Screening tests such as measuring visual acuity, color blindness and monitoring Macular Degeneration are carefully designed to require particular visual parameters such as proper distance of displayed symbols from the subject, or the proper orientation of the displayed symbols. As such, any self-administered visual test must be able to reasonably ensure that the test is properly administered from user to user with consistency.
The present invention has been conceived with the aim of addressing one or more of the aforementioned problems. More specifically, the present invention boosts a subject's ability to accurately and confidently self-monitor their vision in any environment, which enables improved detection of eye disease symptoms. Self-tests and monitoring enhances a subject's ability to seek an eye care professional at an earlier stage of the condition, which enables earlier clinical diagnosis of onset or progression of diseases as well as earlier start of treatments. As a result, routine eye health evaluation is promoted and ultimately fewer people experience suboptimal vision and unnecessary vision impairment or vision loss.
Currently, there are several competitive mobile applications, which also attempt to measure visual acuity. The majority of these applications are deficient in that they are mostly static eye charts without any dynamic self-administration algorithm which correctly measures one's visual acuity. When the eye charts are static, the variation in distance is fixed (typically 20 feet) and it becomes cumbersome to administer the test by the user himself. Specifically, it almost always requires an additional person to help assist in determining if user is identifying the optotypes correctly. In addition, the visual acuity cannot be determined accurately without an algorithm. The present invention disclosed herein, however, avoids the problem discussed above, as well as providing other improvements. Likewise, the field is in shortage of effective portable solution which allows an user to self-administer color blindness screening examination using a mobile computing device. Furthermore, the current art is also deficient in effective portable solution which allows an user to self administer macula degeneration screening examination using a mobile computing device.